Noise parameters typically include a set of values that describe how the noise figure of a device varies with impedance match. The noise parameters generally vary with conditions associated with a device-under-test (DUT), such as frequency, bias, or temperature. There are different forms of the noise parameters, but generally may include a set of four (4) scalar values. A commonly used set is:
1. Fmin=minimum noise FIG.
2. Gamma_opt magnitude=magnitude of gamma_opt, the optimum source gamma that will produce Fmin
3. Gamma_opt phase=phase of gamma_opt, the optimum source gamma that will produce Fmin
4. rn=equivalent noise resistance, which determines how fast the noise figure will change as the source gamma moves away from Gamma_opt.
With this set of noise parameters, the noise figure of the device for any source impedance is then generally described by the equationF=Fmin+4*rn*|gamma_opt−gamma—s|^2/(|1+gamma_opt|^2*(1−|gamma—s|^2))Where
gamma_s=source reflection coefficient seen by the DUT
F=Noise figure
Other noise parameter forms include a correlation matrix (of which there are multiple configurations), and a set with forward and reverse noise used by the National Institute for Standards and Technology (NIST). Generally, all of the noise parameter forms contain the same basic information. So if one form of the noise parameters is known, the noise parameters can be converted to any other form with a math formula.
Noise parameters are typically measured by measuring the DUT under multiple impedance conditions, in a setup similar to that shown in FIG. 1.
The traditional measurement method is to:
1. Make the preliminary system calibrations and measurements, as needed. This typically includes calibrating the measurement system s-parameters, including the tuner or tuners, so that it can later be de-embedded from the DUT measurements.
2. Calibrate the noise receiver parameters, so that the noise receiver can later be de-embedded from the DUT measurements. This is typically done per the flow diagram in FIG. 2 as follows:
a. Measuring the data at one impedance state at a time until one frequency is complete.
b. Go to the next frequency, and repeat step a. The set of tuner states to be used for the noise receiver calibration will typically vary from frequency to frequency. Usually, frequency is the only sweep parameter used for the noise receiver calibration, because other parameters that affect the DUT, such as DUT bias or DUT temperature, do not affect the noise receiver.
3. Measure the needed data with the DUT in place per the flow diagram in FIG. 3, as follows:
a. Measure the needed data at one tuner state at a time until the data collection is complete at one sweep parameter value, such as frequency. From this, the noise parameters can be determined for that sweep parameter value. Instead of frequency, the sweep parameter can also be other conditions that affect the DUT performance, such as bias or temperature.
b. Repeat the measurement in step a for each sweep parameter value of interest. The set of tuner states to be used for the DUT measurement will typically vary from one sweep parameter value to the next, as the set of multiple source impedances is typically determined independently at each swept value.
A significant limitation of the prior art is the overall measurement time. This can include setup time, tuner calibration, system calibration, receiver calibration, as well as the DUT measurement.